Filtering assemblies serve for the filtration of liquids, for example, in the form of hydraulic power oil or solutions of that type, for example in the form of genuine suspensions, dispersions, emulsions or colloidal solutions. Such filtering assemblies have generally proven themselves reliable in use on account of their compact structure and their large filter surface. In order to guarantee that the fluid flow passes only through the proper filter medium, on the two end caps, the connection point of the two ends of the filter mat are adjacent to one another and adjacent to the seal, and are in the form of terminal webs or crosspieces to form one of the critical points which are to be closed off without leakage.
The known filtering assemblies available on the market today have a zigzag-folded or pleated filter mat composed of different filter materials for use under different circumstances. The filter mat is arranged around a solid support pipe arranged in the interior of the filtering assembly and provided with apertures. A fine-mesh wire netting encloses the filter mat to protect it from damage from the exterior. The netting is contiguous with and follows the folding path of the filter mat. In the case of the known filtering assembly, the connection point of the two filter mat ends, the same as the connection of the filter mat with the end caps, is attained by application of an adhesive layer, for example epoxy resin adhesive. Dependent upon the adhesive being used, considerable waiting time is required during the further processing or further use of the filtering assembly, until the adhesive following its gelling or cure time can be further processed and then placed under the stress of use and until it can be used again following its hardening time.
With one known tubular filtering assembly, disclosed in EP 0 695 211 B1, because of improved handling and an increased stress capacity, the filter mat is surrounded on its exterior by a metal mesh covering. The covering protects the filter mat with its small mesh width. In an adhesive layer, for example formed by a two-component adhesive, the components are embedded in one another and turned toward each other. The rounded-off end of the metal mesh covering holds the ends of the filter mat between them. A cradle-like metal clamp can be provided as further limitation for the adhesive layer. The ends of filter mat and metal mesh covering engage to produce the connection point. Also, with this solution, the gelling and hardening times of the adhesive being used are to be taken into consideration in the case of further processing of the filtering assembly.
Additionally, the use of adhesives in the connection device for the filter mat ends requires special devices to be arranged on the side of the device. Such special devices prevent undesired discharge of adhesive from the connection seam. The maintenance of such special devices is costly and provides another measure of the increased production costs.
A tubular filtering assembly of this type is disclosed in EP 0 001 407. The filter mat ends are welded with one another by means of a longitudinal seam clip configured as a connection device to avoid the use of the adhesive material and to avoid the manufacturing costs involved therewith. The free arms of the known clip are configured to be elastically flexible. They can be spread apart upon thrusting of the filter mat ends therein, and can exert, on these ends, the degree of pressure required for the fixing. At the point of the transition of the two free arms of the longitudinal seam clip, this clip forms a sort of shoulder. The free ends of the filter mat engage the shoulder and/or are limited in the direction of thrusting into the clip. The filter mat ends then terminate flush with one another and assume the definitive position required for production of the weld connection. The arrangement cannot lead to being damaged and discarded. However, particularly with highly stressed filtering assemblies, such a weld seam connection can tear apart and can lead to a breakdown of the filtering assembly or even to a hydraulic volume build-up, in which the resulting filtering assembly is worn down.